Computer systems almost exclusively include a screen for displaying data. Highlighting of that data or control of the computer system is in part achieved through the use of a cursor. The cursor is moved through the use of a mouse or roller ball connected to the computer system. A user uses the mouse or roller ball to move the cursor. Many computer systems allow the cursor to move unfettered across the whole of the screen.
When using a graphic program which displays data in a graphical manner, it is often difficult to maintain control of the cursor. In particular, when a user attempts to draw a straight line using the cursor, it is difficult to control the cursor sufficiently accurately. The consequence is often not a straight line but one with steps of one or more pixels.
Hitherto, it has been proposed to control the cursor by locking movement of the cursor in a straight line. Such control has been provided using keyboard control or menu control. However, this type of control is cumbersome. First of all, a user must implement the locking control by using the keyboard or using an option from the menu. Secondly, locking the cursor does not allow interactive variations to determine whether a straight line is required or not because the cursor may only be used to display a straight line.